桥梁主梁断面18个颤振导数识别的三自由度强迫振动法

Three degrees-of-freedom forced vibration method for identifying eighteen flutter derivatives of bridge decks

利用开发的全数控三自由强迫振动装置,发展桥梁断面18个颤振导数识别的三自由度强迫振动法。强迫振动装置的驱动系统由伺服电机、数字驱动器和独特的耦合运动机构共同组成,实现由电脑调节振动频率等参数及控制其各个自由度单独或耦合运动;采用时域最小二乘识别算法,通过单自由度、竖向和扭转两自由耦合以及三自由度耦合三种运动方式分别对宽厚比为1/22.5的平板断面以及两种典型的桥梁断面进行颤振导数识别。试验结果表明,该方法识别的平板断面颤振导数与Theodorsen理论值非常接近;桥梁断面颤振导数曲线比较光滑,与阻力有关的颤振导数也具有良好的趋势性,而且模型运动方式对桥梁断面颤振导数的影响很小。

A three degrees-of-freedom （3-DOFs） identification method was developed to extract 18 flutter derivatives of bridge decks by utilizing the digitally-controlled forced vibration device. The developed forced vibration device consisted of servo motors, digital drivers and a special coupled motion mechanism. The frequency of motions and the motion patterns in terms of single DOF vibration or coupled muhi-DOFs vibration were simply controlled by computers. Based on the measured model displacements and the aerodynamic forces exerted on the model, the flutter derivatives of a thin-plate section with a thickness to width ratio of 1/22.5 and other two typical bridge deck sections were identified in time domain. The effect of motion patterns on identification results was discussed. The results show that the identified flutter derivatives of the thin-plate section agree rather well with the theoretical values of thin airfoil given by Theodorsen. The identified major flutter derivatives of the two typical bridge decks demonstrate regular variation patterns with the reduced wind speed. Moreover, the flutter derivatives associated with drag forces generally show good trends, and the motion pattern of the models has little effect on the flutter derivatives of bridge decks.